Stop the outbreak
A small town, 300 people, one visitor with a very contagious illness. Guess what happens, watch it spread, then use vaccination, hand-washing and staying home to make the outbreak shrink.
Herd immunity, in plain words
When enough people are immune, a germ keeps running into dead ends. Each sick person passes it to fewer than one new person, and the outbreak fades out.
R0 is the average number of people one sick person infects when nobody around them is immune. Measles is one of the most contagious diseases known: its R0 is commonly cited as 12 to 18.
If R0 is 12, then 1 − 1/12 ≈ 92% of people need to be immune to stop the spread. For a germ with an R0 of 2, it's 50%. The more contagious the germ, the higher the bar.
No vaccine protects every single person. Two doses of the measles vaccine protect about 97 in 100 people. So WHO says at least 95% of people need to be vaccinated to keep measles out.
Babies too young for the vaccine, and people whose immune system is weak because of illness or treatment, rely on everyone around them being immune.
Three things that slow a germ down
The UAE's National Immunisation Programme, run by the Ministry of Health and Prevention (MOHAP) and the local health authorities, includes the measles vaccine (MMR) in the routine childhood schedule. Check your family's vaccination record, and ask your health centre or doctor if a dose was missed.
Washing with soap helps most against colds, flu and stomach bugs. Measles mostly spreads through the air, so for measles the vaccine is the main protection.
It keeps germs away from classmates and colleagues. But people with measles can pass it on for about 4 days before the rash appears, which is why staying home alone can't stop it. If you think someone has measles, call the clinic before you go, so they can protect others in the waiting room.
Hand-washing, step by step
- Wet your hands with clean running water
- Lather with soap: backs, between fingers, under nails
- Scrub for at least 20 seconds
- Rinse well
- Dry with a clean towel or let them air-dry
Best times: before eating or cooking, after the toilet, after coughing or sneezing, and when you get home from the mall, the metro or school.
About this simulation
This is a simplified "SIR" model: each dot is susceptible, infected, or recovered (or protected by a vaccine). Dots catch the illness by chance when they're close to a sick dot. The measles-like illness is set so one sick person infects about 12 others in a town where nobody is immune, the low end of the commonly cited range. Real towns, real people and real diseases are far more complicated, so the numbers here are an illustration, not a forecast.
Sources: US CDC measles pages (up to 9 in 10 people who are close to someone with measles and not immune will catch it; people can spread it from 4 days before to 4 days after the rash; two doses of MMR are about 97% effective); WHO measles fact sheet and WHO Europe's herd immunity guidance (at least 95% coverage needed); Guerra and colleagues, "The basic reproduction number (R0) of measles: a systematic review" (Lancet Infectious Diseases, 2017), and standard epidemiology texts for R0 12–18 and the 1 − 1/R0 threshold; CDC hand-washing guidance (scrub at least 20 seconds; hand-washing cuts respiratory illnesses such as colds by about 16–21%); UAE Ministry of Health and Prevention, National Immunisation Programme. This page is for learning, not medical advice. For vaccination questions, talk to your doctor or health centre.